New Horizons Flyby Modeling ChallengeResults from a 1D gasdynamic model of the Solar Wind propagating from the inner heliosphere
to Pluto from Peter MacNeice and Nathan Schwadron
This model solves the 1D gasdynamic equations for the Solar Wind. It includes estimates for
enhancement of the wind mass density due to photoionization of neutral hydrogen entering the
heliosphere from the interstellar medium. It also includes the drag effect and associated heating
of the wind caused by charge exchange between protons in the solar wind and the neutral
hydrogen (producing the so called Pick up ions). These source terms for these effects are implemented
as in Schwadron et al (2011), Ap.J. volume 731:56. The distribution of neutral hydrogen has been set in accordance with the analysis of New Horizon SWAP measurements reported in Randol et al (2012), Ap.J. volume 755:75.

Click here to download this movie in animated gif format
The left panels show the wind evolution as a function of radius. The vertical blue line indicates
the radial location of Pluto. The right panels show the wind properties as a function of time at Pluto.
The blue dot indicates the value at the time of the New Horizon flyby.
This simulation is driven by the OMNI measurements of the Solar Wind in the 'near Earth' environment
at 1AU. These observations have been shifted in time to account for the time varying difference in heliospheric
longitude between the Sun-Earth and Sun-Pluto directions.

Click here to download this movie in animated gif format
This second graphic shows results from the same model, but with the addition of an estimate of the additional
heating due to dissipation of turbulent fluctuations in the magnetic field and solar wind velocity. These affects
are modeled following the description in Adhikari et al (2014), Ap.J. volume 793:52. In this case we include
the additional driving of the turbulence by the Pick Up ion population. This graphic shows results for the case
in which this term is most effective, ie where the fraction of the pick up ion energy transferred to excited waves
is largest (fd=1.0) and full mixing of incoming and outgoing waves (Γ=1.0).